A Study of Cysteine Desulphydrase in Certain Insects

Abstract

An enzyme capable of liberating H2S from l-cysteine in vitro (cysteine desulphydrase) is present in insect tissues. The clothes moth (Tineola bisselliella Humm.) has a highly active desulphydrase apparently concentrated in the gut, whilst some other insects have little or no activity. Aqueous enzyme solutions from insects are unstable, their optimum pH ranges between pH 7·8 and 8·9, they are inhibited by NaCl and KN03 (both at 0·42M), and Asps, NaHS03 , and phenylhydrazine (all at 10-2M), but they are not affected by semicarbazide, thiourea, sodium pyrophosphate, or sodium fluoride (all at 1O-2M). KCN (10- 2M) activates clothes moth preparations, has no effect on those of carpet beetle, and inhibits some other insect enzymes.